This invention relates to computer hard disk drives, and more particularly relates to apparatus and methods for writing servo patterns on a hard disk.
In computer hard disk drives an arrangement of so-called servo patterns is magnetized into the disk prior to the time a user is to use the drive to store data. These servo patterns are arrayed as fields throughout the disk, typically one servo field in each sector of each track. Data are recorded on the tracks in the segments between the servo fields.
The servo fields have a predetermined pattern of magnetization, typically in the form of the well known A, B, C, D burst patterns. When the disk drive is initialized, the head performs a seek operation over these servo fields. When the servo fields are located, the predetermined pattern is used by the servo system of the disk drive to center the head on a particular track so that data may be written to and read from the disk with the required precision.
Servo patterns are currently written to the disk with a machine called a servo writer. The way in which the servo writer operates is as follows. Near the end of the manufacturing process, each hard disk is placed in the servo,writer to embed the servo patterns onto each platter in the drive. Through a hole in the side of the hard disk drive base plate, a laser measurement system determines the precise location of the read/write head. This position information is fed into a control system that positions the read/write head at the correct location for each stage of the servo pattern writing process. Since the A, B, C, D burst patterns for adjacent tracks are interlaced, the read/write head must make several passes to write the servo pattern for each track. This servo pattern writing process is very time consuming, due to the fact that the process must be repeated for each track on both sides of each platter in the hard disk drive.
The servo writer is an expensive piece of equipment, with the current cost being in the range of $300,000. This cost is added to manufacturing cost. In addition, the servo writer can only operate on one hard disk at a time, which slows the manufacturing time and further increases manufacturing cost. Now, the number of concurrent assembly lines in a hard disk drive manufacturing plant determines the capital cost. However, it is believed that the manufacturing time taken to write the servo pattern in each drive constitutes an even larger cost.
If the writing of servo patterns could become a parallel manufacturing process, the cost of writing servo patterns could be significantly reduced. In addition, if the servo writer could be eliminated altogether, such costs could be reduced even more.
Attempts have been made to provide automated servo pattern writing. One example is found in U.S. Pat. No. 5,012,363, which issued to Shingi Mine et al., on Apr. 30, 1991, and which was assigned to International Business Machines Corporation. However, the technique described in this patent requires that one disk be written with a servo pattern prior to the assembly of the disk drive unit, i.e., by an external servo writer unit. In addition, the invention calls for the same head to be used for both reads and writes.
Another prior art attempt is described in U.S. Pat. No. 5,570,247, which issued to Dana H. Brown et al., on Oct. 29, 1996, and was assigned to International Business Machines Corporation. However, the technique described in this patent is similar to that described in the ""363patent, and suffers the same limitations.
Another prior art attempt is described in U.S. Pat. No. 5,612,833, which issued to Edward J. Yarmchuk et al., on Mar. 18, 1997, and was assigned to International Business Machines Corporation. However, the technique described in this patent is similar to that described in the ""363 and ""247 patents. In addition, this technique requires the storage of reference values for the position error signal (xe2x80x9cPESxe2x80x9d) offset in a lookup table. For servo writing, it calls for use of a proportional, integral, derivative (xe2x80x9cPIDxe2x80x9d) servo loop having a closed loop gain of less than one at integer multiples of the spindle frequency.
Another prior art attempt is described in U.S. Pat. No. 5,793,554, which issued to Timothy Chainer et al., on Aug. 11, 1998, and was assigned to International Business Machines Corporation. However, the technique described in this patent is similar to that described in the ""436, but adds a correction component to the stored lookup table value.
Another prior art attempt is described in U.S. Pat. No. 5,793,559, which issued to Stanley H. Shepherd et al., on Aug. 11, 1998, and was assigned to Quantum Corporation. However, the technique described in this patent attempts to make servo pattern error corrections at data read/write, based on error data recorded after servo write.
Another prior art attempt is described in U.S. Pat. No. 5,844,742, which issued to Edward John Yarmchuk et al., on Dec. 1, 1998, and was assigned to International Business Machines Corporation. However, the technique described in this patent is similar to that described in the ""833 and ""436 patents, but adds the disclosure of adjusting the nominal servo loop reference value by 2/3 of the A=D servo position, due to the use of separate read and write heads, to align the write head during servo writing. Also, the effects of TMR are reduced by adjusting the write time of the burst pattern.
Another prior art attempt is described in U.S. Pat. No. 5,875,064, which issued to Timothy Chainer et al., on Feb. 23, 1999, and was assigned to International Business Machines Corporation. However, the technique described in this patent is similar to that described in the ""436, adding a refinement.
The present invention overcomes the limitations of the prior art.
The present invention provides, according to one aspect, a method for writing servo patterns on a disk in a hard disk drive assembly. The assembly includes a disk having at least one magnetic surface in which a reference pattern has been written, determining a reference track. Also included is an actuator having a shaft engaged with the disk to provide rotational motion to the disk, an actuator arm, and a micro-actuated read/write head mounted on the actuator arm. The method includes the following steps. First, the read/write head is used to position the actuator arm at a first fixed position over the reference track. The actuator arm is maintained at the first fixed position while the read/write head is used to write a second servo pattern, determining a second track. The read/write head is used to position the actuator arm at a second fixed position over the second track. Then, the actuator arm is maintained at the second fixed position while the read/write head is used to write a third servo pattern.
According to another aspect of the present invention, there is provided a method for writing servo patterns on a disk in a hard disk drive assembly, wherein the assembly includes a disk, rotatable about a central axis thereof, having at least one magnetic surface. Also included is an actuator having a shaft engaged with the disk to provide rotational motion to the disk about the central axis. An actuator arm is provided, capable of lateral movement across the surface of the disk for positioning over substantially circular tracks thereon. A micro-actuated read/write head is provided on the actuator arm. A mechanical stop is also included for restraining the actuator arm from lateral movement at a predetermined reference position. The method according to this aspect includes the following steps. First, the actuator arm is positioned at the predetermined reference position against the mechanical stop. The actuator arm is maintained at the predetermined reference position while the read/write head is used to write a reference servo pattern, determining a reference track. The read/write head is used to position the actuator arm at a first fixed position over the reference track. The actuator arm is maintained at the first fixed position while the read/write head is used to write a second servo pattern determining a second track. The read/write head is used to position the actuator arm at a second fixed position over the second track. Then, the actuator arm is maintained at the second fixed position while the read/write head is used to write a third servo pattern.
According to a further aspect of the present invention, there is provided a method for writing servo patterns on a plurality of disks in a hard disk drive assembly, wherein the assembly includes a plurality of disks, each having at least one layer of magnetic medium on a surface thereof to form a magnetic surface. The assembly also includes an actuator having a shaft engaged with the disks to provide rotational motion to the disks. Also included in the assembly is a plurality of actuator arms, one associated with each of the magnetic surfaces, and a micro-actuated read/write head on each of the actuator arms. The method includes the following steps. First, a reference servo pattern is written, determining a reference track in at least one of the magnetic surfaces using a write apparatus external to the hard disk drive. A first read/write head of a first actuator arm is used to position the first actuator arm at a first fixed position over the reference track. The first actuator arm is maintained at the first fixed position while a second read/write head of a second actuator arm is used to write a second servo pattern determining a second track.
According to still another aspect of the invention there is provided a method for writing servo patterns on a plurality of disks in a hard disk drive assembly, the assembly including a plurality of disks, each having at least one layer of magnetic medium on a surface thereof to form a magnetic surface. The assembly also includes an actuator having a shaft engaged with the disks to provide rotational motion to the disks, a plurality of actuator arms, one associated with each of the magnetic surfaces, and a micro-actuated read/write head on each of the actuator arms. A mechanical stop is included for restraining a first one of the actuator arms from lateral movement at a predetermined reference position. The method includes the following steps. The first one of the actuator arms is positioned at the predetermined reference position against the mechanical stop. The first one of the actuator arms is maintained at the predetermined reference position while using the read/write head on the first one of the actuator arms to write a reference servo pattern, determining a reference track. The read/write head of the first one of the actuator arms is used to position the first actuator arm at a first fixed position over the reference track. Then, the first actuator arm is maintained at the first fixed position while a read/write head of a second actuator arm is used to write a second servo pattern determining a second track.
According to yet another aspect of the present invention, there is provided a method for writing servo patterns on a disk, including the following steps. A disk is provided, having at least one magnetic surface in which a reference pattern for a reference track has been written. An actuator is provided, having a shaft engaged with the disk to provide rotational motion to the disk. An actuator arm is provided, as is a dual read/write head assembly on the actuator arm having a first head having at least read capability, and having a second, micro-actuated head having read/write capability. The first head is used to position the actuator arm at a first fixed position with the first head over the reference track. The first head is used to maintain the actuator arm at the first fixed position while the second head is used to write a second servo pattern determining a second track. The second head is used to write further servo patterns determining further tracks. The first head is used to position the actuator arm over a track determined by one of the servo patterns written by the second head. Then, the second head is used to write further servo patterns determining further tracks.
According to still another aspect of the invention there is provided a method for writing servo patterns on a disk in a hard disk drive assembly, the assembly including a disk, rotatable about a central axis thereof, having at least one magnetic surface. Also included is an actuator having a shaft engaged with the disk to provide rotational motion to the disk about the central axis. An actuator arm is included, capable of lateral movement across the surface of the disk for positioning over substantially circular tracks thereon. A dual read/write head assembly is included on the actuator arm having a first head having at least read capability, and a second, micro-actuated head having read/write capability. A mechanical stop is also included, for restraining the actuator arm from lateral movement at a predetermined reference position. The method includes the following steps. The actuator arm is positioned at the predetermined reference position against the mechanical stop. The actuator arm is maintained at the predetermined reference position while the first head is used to write a reference servo pattern, determining a reference track. The first head is used to position the actuator arm at a first fixed position with the first head over the reference track. Then, the first head is used to maintain the actuator arm at the first fixed position while the second head is used to write a second servo pattern determining a second track. The first head is used to position the actuator arm at a second fixed position with the first head over the second track. Then, the first head is used to maintain the actuator arm at the second fixed position while the second head is used to write a third servo pattern.
According to still another aspect of the invention there is provided a method for writing servo patterns on a plurality of disks in a hard disk drive assembly, wherein the assembly includes a plurality of disks, each having at least one layer of magnetic medium on a surface thereof to form a magnetic surface. Also included is an actuator having a shaft engaged with the disks to provide rotational motion to the disks. A plurality of actuator arms are provided in fixed spatial relation with respect to one another, one associated with each of the magnetic surfaces. A dual read/write head is mounted on each of the actuator arms, each of the dual read/write heads having a first head having at least read capability, and having a second, micro-actuated head having read/write capability. The method includes the following steps. A reference servo pattern is written, determining a reference track in at least one of the layers of magnetic medium, using a write apparatus external to the hard disk drive. A first head of a first actuator arm is positioned over the reference track, and a second head of one of the actuator arms is positioned at a position suitable for writing a second servo pattern determining a second track on one of the layers of magnetic medium. The second servo pattern is written. The second head is positioned at additional positions for the writing of further servo patterns determining further tracks in the layers of magnetic medium and writing the further servo patterns. The first head is positioned over a track determined by the servo patterns written by the second head. Then, a second head of one of the actuator arms is positioned at additional positions for the writing of further servo patterns and writing the further servo patterns.
According to still another aspect of the invention there is provided a method for writing servo patterns on a plurality of disks in a hard disk drive assembly, the assembly including a plurality of disks, each having at least one layer of magnetic medium on a surface thereof to form a magnetic surface. The assembly also includes an actuator having a shaft engaged with the disks to provide rotational motion to the disks, and a plurality of actuator arms in fixed spatial relation with respect to one another, one associated with each of the magnetic surfaces. A dual read/write head is included on each of the actuator arms, each of the read/write heads having a first head having at least read capability, and having a second, micro-actuated head having read/write capability. A mechanical stop is included, for restraining a first one of the actuator arms from lateral movement at a predetermined reference position. The method includes the following steps. First, the first one of the actuator arms is positioned at the predetermined reference position against the mechanical stop. The first one of the actuator arms is maintained at the predetermined reference position while using a first head of one of the actuator arms to write a reference servo pattern, determining a reference track. The first head of the one of the actuator arms is positioned over the reference track. A second head of one of the actuator arms is positioned at a position suitable for writing a second servo pattern determining a second track on one of the layers of magnetic medium. The second servo pattern is written. The second head is positioned at additional positions for the writing of further servo patterns determining further tracks in the layers of magnetic medium and writing the further servo patterns. A first head of one of the actuator arms is positioned over a track determined by the servo patterns written by the second head. A second head of one of the actuator arms is positioned at additional positions for the writing of further servo patterns and writing the further servo patterns.
These and other aspects and features of the invention will be apparent to those skilled in the art from the following detailed description of the invention, taken together with the accompanying drawings.